Fireproofed wood and process of treating wood



many radiator, or rain driving Patented Nov. 5, 1929- v UNITED sures PATEN orrlce eosnrn a. coonmen, 3D, or nnooxrmn, masse'cnusn'r'rs, assrenon 'ro mourn,

INC., OF'BOSTON, MASSACHUSETTS, A. CORPORATION OF rrnnrnoornn 80 Drawing.

This invention wood to render it highly resistant to combustion. The invention involves both a novel process and also a new product.

The natural inflammability of wood is aobjection to its use for man for example, for interior finis in modern buildings of the In fact, the authorities in cities where every effort is being made to reduce the fire hazard have adopted very strict regulations as to the fireproof properties of flooring used in such buildings.

The most successful methods so far devised of treating wood to render it fireproof consists in impregnating the wood with certain water soluble salts, ammonium chloride, ammonium sulphate, borax, and the like, being commonly used for this-purpose. These treatments, while effective from the fireproofing standpoint, are objectionable in certain other res ects. For example, an especially serious 0 jection is the fact that the salts absorb moisture from the atmosphere in damp weather, notwithstanding the presence of finish coatings of varnish, shellac, or the like,-and the solution resulting from such absorption sometimes attacks the finish, and in any event leaves discolored spots or streaks on the floor or finish which are highly objectionable from a standpoint of appearance. If water stands on such a floor for any length of time, as for example, water leaking from a in through an open window, the action on the salts with which the wood is impregnated is even more pronounced. Furthermore, when woods fireproofed with salts are used in locations such as cellars, basements, or the like, where, while not exposed to the weather, theless, exposed, to considerable dampness, they gradually lose their salts due to the action of the moisture. gree of fire protection afiordedb this treatment is not permanently retaine ally is reduced.

very serious purposes, as or for flooring fireproof type.

The present invention deals with the prob by these conditions, and 1t lems presented method of fire roofing wood aims to devise a which will overcome relates to the treatment of I j cylinder of Consequently, the de-' in the wood. As above stated, however,

but graduthe objectrons'above tie-"kind of wool being treated, an

woon Ann raocnss or rename woonf Application filed December 18, 1926..' Serial $0,155,736.

scribed. It is also an important object of this invention to produce a wood fireproofed to such a degree as to meet the very severe reqmrements of authorities such as the underwriters laboratories, while at the same time protecting the fireproofing material from atmosphericaction, and holding said material more effectively in possible heretofore. According to this invention the wood is impre nated with fireproofing materials of any suitable character, and a protective agent is associated with the material which reve'nts the deleterious action above descri ed.

According to the preferred process the wood is first impregnated with a suitable fireproofing 'material such as ammonium salts, borax, and the like, such material being hereinafter referred to as salts. I have obtained particularly satisfactory results by mixing ammonium chloride and borax in equal parts, and then dissolving one part, by weight, of this mixture of salts in two parts, by weight, of water. The impregnation with these fireproofing salts may be performed in any convenient manner, this part of the process beingwell known in this art. Assuming, for example, treatment is redoak, an entirely y immersing the wood in the salt solution and maintaining a pressure of approximately 200 lbs. per square inch on the solution for one hour, the solution being held at afairl hi h temperature, as for example, 190 1 pressure the type used in-impregnating wood'is required for this purpose. At the end of the period of one hour just mentioned it is preferable to cut ofi the steam and then they are, never- Ito circulate cold water throu h the steam heating coils in the cylinder. his operation should be continued for about an hour, the cooling of the solution precipitating the salts the impregnation of the wood with fireproofing salts may be accomplished in any suitable manner,

on the equi ment available, the size of t 'eieces, t e

the like.

the wood than has been that the wood, under and the procedure adopted necessarily will depend somewhat u If the impregnation is performed at high temperatures, there is considerable tendency to darken the wood, but this discoloration can be reduced or entirely avoided by reducing the temperatures at which the impregnation with the salts is performed. A high temperature followed by cooling, as above described, is, however, a convement method of introducing a high concentration of salts in the wood.

A certain amount of the water should next be removed from the wood in order to make room for the material which is to seal the salts in the wood. Thismay be accomplished either by subjecting'the wood to a vacuum while it still remains in the treating cylinder, or the wood may be removed and artially dried. Assuming that the wood un er treatment is red oak, the weight of the wood is approximately doubled by the treatment above b described, about two-thirds of this increase in Wei ht being water and one-third salt. It is pref rable to reduce this water content at least 15% before proceeding with the next step of the process. .Whether this is done by air or kiln drying, or by subjecting the wood to a vacuum while still in the cylinder, will depend largely upon conditions obtaining at the treating plant.

The discovery of a suitable material for holding the salts in the wood them from the action of external moisture, without at the same time decreasing the fireproofing properties of the final product, has

roved to be a very difficult matter. After a ong series of experiments, however, I have found that ordinary soap satisfies these requirements. Accordingly, the next step in this process preferably consists in impregnating the wood which has now' been treated with fireproofing salts and then partially dried, with a. solution of, say, one part of soap in five. parts of water. The impregnation should be performed in a pressure cylinder, the solution being maintained at, say, 150 F. and forced into. the wood under approximately 200 lbs. of pressure for a period of one hour. The woodthen is removed from the cylinder and stacked when it can drain and dry out.

When the wood hasdried it has an ap earance substantially like untreated woo and is entirely devoid of the discolored surface which is a characteristic'of wood fireproofed by the usual processes. This surface takes the ordinary finishes, such as varnish, waxes, or the like, entirely satisfactorily. I have had no difficulty in treating wood by this process so that it sucessfully passed the tests scribed by the underwriters laboratories. An important advantage of wood fireproofed in this manner as distinguished from that treated by prior processesis that it retains its fireproof characteristics indefinitely, whereas wood treated by the common commercial procand protecting preafforded by the treatment esses gradually loses its fireproof characteris tics under many conditions of use.

While the action which takes place in the wood is somewhat obscure, it seems clear that the impregnation with the fireproofing salts results in the deposit of these salts on and in the walls of the pores and tracheids of the wood. The subsequent impregnation with soap results in coating the walls with this a terial, some of the soap solution probably also entering the cell walls. This coating thereafter protects the salts from the action of external moisture under ordinary conditions. The presence of the salts has the apparent effect of reducing the solubility of the soapso that the soap in the treated wood is not read-,

ily acted upon by water. to be partly converted into ety due to the presence of The soap appears the insoluble variimpurities in the orax. In any event, the soap assumes a rubbery consistency and becomes relatively insoluble, acting much as it does in sea water min a strong brine.

While the foregoing is the best explanation of the favorable results obtained which I am able at this time to give, it will be understood that the invention is not limited to the theory above set forth.

s 'above stated, I have obtained very satisfactory results by using ordinary hard laundry soap of the tallow or tallow and resin variety. The of the soap may, however, be further increased by adding to the soap solution a small proportion, say 25% of the weight of the soap, of some material such as paradichlorbenzene. The soap impregnation, particularly when a small proportion of paradichlorbenzene is used with it, has considerable merit as a fireproofing agent, although it does not afford the same degree of protection as the treatment above described.

As a further variation of this method, "I may use some material, such. as calcium chloride, aluminum sulphate, or the like, either with or without other salts, in effect ing the first impre ation, the salts mentioned combining with the soap to form in the wood an insoluble soap that will act as a sealing agent. In fact, some action of this character ap ears to take place in the process above descri ed. Also, the entire body of soap may be formed in'the wood by ingredients forced into the wood in successive impregnations. While, therefore, I prefer to use the method described in detail above, it will be evident that the method is susceptible of considerable variation without de arting from the essential features thereof. 'lh fact, for many purposes it is not necessary to impart to the wood the degree of fire protection above described, and in such cases the treatment may be suitabl modified.

his application and my pending applicafireproofing properties soap tion Serial No. 181,276, filed April 5, 1927, have certain features in common, and the claims on the common subject matter are presented in thelatter application. The claims in this application are confined to features which are not claimed in the later application just mentioned.

. Having thus described my invention, what I desire to claim as new is:

1. An article of the character described, comprising wood impregnated with fireproofing salts, and also impregnated for a substantial depth with soap.

2. An article of the character described, comprising wood, the walls of the pores and tracheids of which carry a water soluble fireproofing salt, and a coating of soap on said walls.

3. That improvement in processes of fireroofing wood, which consists in impregnating the wood with water soluble fireproofing salts, and subsequently impregnating the wood with a soap.

4. That improvement in processes of,fireproofing wood, which consists in impregnat- 111g salts, subjecting the wood to a drying oper ation, and-then impregnating the wood for a substantial depth with a water solution of a soap.

5. An article of the character described comprising wood impregnated with a fireproofing salt and also impre ated for a substantial depth with an inso uble metallic which serves as a protective agent for said fireproofing salt. 7 a

6. An article of the character described comprising wood, the walls of the pores and tracheids of which for a substantial depth carry a water soluble fireproofing salt, and an insoluble metallic soap in sai pores and tracheids serving to protect said salt.

7. That im rovement in processes of fireproofing wood which consists in forcing into the pores and tracheids of the wood or a substantial depth'a water solution of a fireproofing, salt, including in said solution a metallic salt adapted to react with a soluble soap to form an insoluble soap, and subsequently' impregnating the wood so treated with a solution of soap to combine in the wood with said metallic salt to produce an insoluble soa capable of sealing said fireproofing salts in t e wood.

J QSEPH R. COOLIDGE, III.

the wood with water soluble fireproofing 

